1. Field of the Invention
The present invention relates generally to signal measurement systems and, more particularly, providing a magnified view of displayed waveforms in signal measurement systems.
2. Related Art
Conventional signal measurement systems such as digital oscilloscopes sample, record and display time-varying analog signals. Samples of an input signal are taken and quantified, and the resultant digital representations are stored in a waveform memory under the control of a sampling clock. The acquired data may subsequently be read out as locations in memory are sequentially addressed by a clock signal to provide digital data which can be converted to a time-varying output signal for a waveform display. The sampling clock may be operated at one of several selectable rates depending upon the frequency content of the input signal. The selection of the portion of the analog input signal which is sampled and stored is determined by appropriate triggering circuitry to enable the operator to display the desired portion of the waveform.
There are many types of display elements which can be presented in signal measurement systems in general and test and measurement instruments in particular. For example, in addition to waveforms representing the signals currently received at channel inputs, waveforms referred to as function waveforms may also be displayed. Function waveforms are waveforms created by processing the signal waveforms. Function waveforms may be created, for example, by performing arithmetic manipulations or combining multiple input signal waveforms. The resulting function waveforms are placed in a system memory for subsequent retrieval and display. In addition, memory waveforms may also be displayed. Memory waveforms are waveforms which have been stored in memory for later display. In addition to the above waveforms, other well-known display elements such as marker indicators, trigger indicators, etc. are typically available for display.
Conventional test and measurement systems typically provide a display grid commonly referred to as a graticule on which the display elements are presented. The display grid divides the coordinate axes into a series of divisions. Waveforms are displayed on the graticule and are scaled vertically and horizontally to facilitate analysis. Typically, the horizontal scale represents sweep speed and is in units of seconds per division. The scale represents signal amplitude and is in units of volts per division. The center of the horizontal axis represents the delay or horizontal position of the displayed waveforms and is referred to herein as horizontal offset. The center of the vertical axis represents the displayed reference voltage of the displayed waveforms and is referred to herein as vertical offset. These parameters are generally referred to as scaling parameters. Thus, there are four scaling parameters which are controlled by the operator to capture a desired portion of a waveform and to achieve a desired relative display of multiple waveforms: horizontal scale, horizontal offset, vertical scale and vertical offset.
A primary function provided of signal measurement systems in the analysis of signals is to enable an operator to magnify the displayed waveforms. Magnified views of desired regions of displayed waveforms allow an operator to easily and accurately determine relative values between the displayed waveforms. Magnified views are also a useful and productive technique for displaying details of a displayed waveform to better understand the behavior of the waveform and its correlation with measured quantities such as peak-to-peak voltage, rise-time, etc. Generally, signal measurement systems display simultaneously two views of a displayed waveform when the operator selects the magnification feature: the original or main waveform display, and the magnified waveform display. When the magnification function is invoked, the main waveform display is typically allocated a portion of the display screen while the magnified waveform display is drawn in the portion of the display screen not occupied by the main waveform display. The magnified waveform display presents a predetermined or selected portion or region of the main waveform display at some expanded scale.
In one conventional approach to providing a magnified view of waveform displays, the waveforms in the selected portion of the main waveform display are rendered in a unique color, commonly dark red. This technique derives from that used in monochrome analog oscilloscopes which used a higher intensity shade for signal waveforms in the selected waveform region. There are a number of drawbacks to such conventional systems. First, when the color of the waveforms is replaced with the selected intensified color, the informational content of the waveform display embodied in the waveform color is lost. Furthermore, it is difficult to distinguish between multiple waveforms rendered in the same intensified color. Also, changing colors of the selected region is not necessarily sufficient to identify the selected portion of the waveforms. This may occur, for example, when the magnified scale is very small relative to the main scale or when the displayed waveforms are very sparse. In such situations there may be an extremely small region rendered in the intensified trace which may be difficult or impossible for an operator to see.
Another conventional approach to providing a magnified view requires the operator to delineate the region of the main view which is to be magnified using vertical markers. This conventional technique is commonly used in monochrome oscilloscopes where the implementation of an intensified trace using different colors or shades is difficult or impossible. This approach, however, is also subject to significant drawbacks. When a large amount of waveform information is presented in the main waveform display, the vertical markers may be indistinguishable from the displayed waveforms and associated information. A large amount of waveform information may be displayed, for example, when running in an untriggered state or when using infinite persistence with multi-valued waveforms. As a result, the extent of the waveform display which is being magnified cannot be easily identified in the main waveform display. This significantly reduces the utility of the magnified waveform display.
What is needed, therefore, is a system and method for generating a magnified view of a waveform display which is graphically associated with a selected region of the main view without compromising the information presented in either view. The system should also provide the operator with the ability to directly control the extent and position of the selected region of the waveform display to be magnified. Such a system should also be simple and uncomplicated to enable an operator to perform magnification operations on displayed waveforms quickly and easily.
The present invention is an apparatus and methodology for use in a signal measurement system having a graphical user interface. In one aspect of the invention, an apparatus constructed and arranged to simultaneously render on a display of pixels a main waveform display and a magnified waveform display is disclosed. The main waveform display is adapted to have displayed therein one or more waveforms and associated data on a first graticule with a background while the magnified waveform display is adapted to have displayed therein a magnified view of a region of the main waveform display on a second graticule with a background. The region of the main waveform display to be magnified is defined by a graphically-controllable selection window positioned over the main waveform display to encompass the region. Preferably, the operator-controllable selection window has a position and extent that may be graphically manipulated.
In one embodiment, the apparatus includes a magnification selection window determinator constructed and arranged to determine horizontal and vertical scale and offset values of the magnified waveform display. These values are related to a position and extent of the selection window. In this embodiment, the apparatus also includes a rendering controller constructed and arranged to control a rendering of the main waveform display, the magnification waveform display and the selection window based upon the horizontal and vertical scale and offset values. In one embodiment, the rendering controller is further constructed and arranged to control the rendering of the main waveform display, the magnification waveform display, and the selection window based upon a graphical mode of the display of pixels. Preferably, the rendering controller is still further constructed and arranged to control rendering of graphical features that associate the magnified waveform display and the selected region.
In one embodiment, the magnification selection window determinator includes a selection window boundary determinator for determining pixel boundaries of the selection window on the display. It also includes a graphical selector for enabling an operator to graphically manipulate the selection window to effect changes in scale and offset values of the magnified waveform display. Preferably, the graphical selector includes a selection window manipulation controller for determining whether the operator has graphically selected the selection window for changing its position or extent, and a hit-tester for determining whether a display element has been graphically selected.
In one alternative embodiment, the selection window manipulation controller determines whether a pixel within a predetermined region of pixels surrounding the selection window has been selected. Selection of a pixel within the predetermined region of pixels is interpreted as a resealing operation such that subsequent changes in a cursor position result in analogous changes in a display location of only one or more of the plurality of selection window sides associated with the selected pixel. Selection of a pixel within the selection window and not within the predetermined region of pixels is interpreted as an offset adjustment operation such that subsequent changes in a cursor position result in analogous changes in location of all of the plurality of selection window sides. Alternatively, xe2x80x9cresizing handlesxe2x80x9d may be used to distinguish whether a pixel on or adjacent to the selection window has been selected with the intent of changing the window""s size or position.
In one further embodiment of this aspect of the invention, the rendering controller includes a windows rendering unit and a graticule rendering unit. The windows rendering unit is configured to generate commands to the graphical user interface to generate windows-related displays based upon the selection window boundaries as well as locations and sizes of the main and magnified waveform graticules. The graticule rendering unit is configured to generate commands to cause a rendering of the main and magnified waveform graticules and associated backgrounds based upon the locations and sizes of the graticules. Preferably, the windows rendering unit generates commands for receipt by the graphical user interface to render the selection window and one or more graphical features that visually associate the magnified waveform display and the selected region of the main waveform display.
In one preferred embodiment, the graticule rendering unit graphically associates the magnified waveform display and the selected display region by generating data to cause a rendering of a background region within the selection region in a first color, the background of the magnification waveform display in the same first color, and the background region of the main waveform display not within the selection window in a second color not the same as the first color.
In another aspect of the invention, an apparatus for use in a signal measurement system having a graphical user interface is disclosed. The apparatus is constructed and arranged to simultaneously display a main waveform display having displayed therein one or more displayed waveforms on a main waveform graticule, and a magnified waveform display having displayed therein a magnified view of a region of the main waveform display rendered on a magnified waveform graticule. The region is encompassed within a selection window positioned over the main waveform display so as to surround the region. The magnified waveform display and the selection window are graphically associated with each other. Preferably, the selection window is rendered on top of the main waveform display so as to surround the selected region, thereby not substantially interfering with information displayed on the main waveform display within the selection window.
In one embodiment, the main waveform display includes a first background region included within the selection window that is rendered in a first color. The magnified waveform display includes a second background region rendered in a second color substantially the same as the first color. The main window also includes a third background region external to the selection window that is rendered in a third color substantially different than the first and second colors.
In another aspect of the invention, a signal measurement system such as a digital oscilloscope is disclosed. The signal measurement system includes a display unit and a graphical user interface for controlling the display unit to provide a pixel display. The signal measurement system also includes a waveform magnification system constructed and arranged to simultaneously display a main waveform display having displayed therein one or more displayed waveforms on a main waveform graticule, and a magnified waveform display having displayed therein a magnified view of a selected region of the main waveform display rendered on a magnified waveform graticule. The selected region is encompassed within a graphically-controllable selection window positioned over the main waveform display so as to surround the selected region while not substantially interfering with information displayed on the main waveform display. Importantly, the magnified waveform display and the selection window are graphically associated with each other.
In a still further aspect of the invention, a method for magnifying a selected region of a main waveform display in a signal measuring system having a display device and a graphical user interface that controls a waveform display region on the display device is disclosed. The method includes the steps of: (a) displaying a main waveform display and a magnified waveform display, wherein the main waveform display includes a first graticule and the magnified waveform display includes a second graticule; (b) calculating a selection window surrounding the selected region of the main waveform display based upon horizontal and vertical scale and offset settings for the main waveform display and the magnified waveform display, and a size and location of the first and second graticules; and (c) graphically associating the magnified waveform display and the selected region of the main waveform display.
In one embodiment, step (a) includes the steps of: (1) rendering the first and second graticules on the waveform display region; and (2) rendering a main view supporting window and a magnified view supporting window. The first and second graticules have a size based upon a current graphical mode of the waveform display region. Also, the main view supporting window and the magnified view supporting window each preferably include display elements associated with control and display of information provided in the associated waveform displays.
In one particular embodiment, step (b) includes the steps of: (1) determining scale and offset settings for the main waveform display and the magnified waveform display; (2) determining main and magnified window display ranges and the scale and offset values based upon the scale and offset settings and a graphical mode of the waveform display region; (3) determining boundaries of the selection window; and (4) rendering the selection window.
In another embodiment, step (c) includes the steps of: (1) rendering a background of the main waveform graticules within the selection window in a first color; (2) rendering a main waveform background not within the selection window in a second color not substantially the same as the first color; and (3) rendering a background of the magnified view window in the first color. Preferably, the second color is chosen such that the contrast between the main waveform background and waveforms rendered in the main waveform display is reduced from that of the selection window.
Advantageously, the present invention enables an operator to directly interact with the displayed waveforms to select a desired waveform display region for magnified viewing. Furthermore, the graphical techniques of the present invention enable an operator to select the scale (extent) and offset (position) of the magnified view quickly and easily. Thus, a graphical approach for directly interacting with the displayed waveforms to select a desired waveform display region for magnification is provided.
Another advantage of the present invention is that the graphical association of the selected waveform region and the magnified waveform display assists the operator in visually correlating the informational content of the main and magnified views of the selected waveform region. This also clearly communicates the relationship between the contents of the main and magnified view windows while retaining all of the information contained in the main waveform display. Thus, an operator may observe all information provided by the implementing system related to the displayed waveforms while simultaneously observing a magnified view of a selected portion of the displayed waveform.
Another advantage of the present invention is that the selection window may be positioned by the operator so as to encompass any desired region of the main waveform display while not degrading or interfering with the informational content present on the main waveform display.
A still further advantage is that the present invention utilizes graphical features to identify the selected region, preserving the separate waveform colors throughout the main waveform display. Furthermore, the selection window is rendered so as to appear on top of the waveform display, making the selected region apparent even when waveform data occupies the entire selected region.
Further features and advantages of the present invention as well as the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings.